jewel.game(function(){
    var dom = jewel.dom,
        $ = dom.$;
        

    // hide the active screen (if any) and show the screen
    // with specified id
    function showScreen(screenId){
        var activeScreen = $("#game .screen.active")[0],
            screen = $("#" + screenId) [0];
    if (activeScreen){
            dom.removeClass(screen, "active");
    }
    dom.addClass(screen, "active");
    
  }
  
      // expose public method
      return{
      showScreen : showScreen
      
    };
 })(); 
   
    